Texas leads the nation in wind energy generation with thousands of wind turbines throughout the state. This is a boon for clean energy generation but not for the state’s large population of bats, which are often drawn to the spinning turbines.
To help discourage them from approaching, Duke Energy Renewables is working with NRG Systems, Inc. to install an innovative bat deterrent system. The technology uses ultrasound to block the sonar that bats use to navigate in the dark, causing them to avoid areas around the wind turbines.
Duke Energy Renewables will install NRG Systems’ Bat Deterrent System over a five-year period at 255 wind turbines at its Los Vientos III, IV and V wind sites beginning in July 2019. This will mark the first commercial deployment of the Bat Deterrent System in the continental U.S.
The Rio Grande Valley, where the Los Vientos wind projects are located, has a robust population of common bat species that provide tremendous pest control benefits to local farmers and ranchers. Maintaining this local bat population was the impetus behind a two-year field study conducted by Duke Energy Renewables, NRG Systems and Texas State University. The study found that the Bat Deterrent System reduced overall bat fatalities by 50% around wind turbine locations at Los Vientos III, IV and V.
“At Duke Energy, we’re focused on generating clean, renewable energy for customers while also protecting the native wildlife around our generation facilities,” said Greg Aldrich, lead environmental scientist with Duke Energy. “With this new technology, we’re pleased that we’ll be able to significantly reduce the impacts on bats and continue our environmental leadership in this area.”
“We are endlessly grateful to the entire Duke Energy team for the crucial role they played in bringing this technology to market,” said Brogan Morton, senior product manager at NRG Systems. “Their participation in the two-year study coupled with their willingness to share their expertise with us helped us create a commercially viable Bat Deterrent System that we expect will have considerable benefits both in terms of wildlife conservation and renewable energy generation. Their implementation of our systems at Los Vientos is the next chapter in what has so far been a successful and rewarding collaboration.”
How the Bat Deterrent System works
The NRG Systems’ Bat Deterrent System is mounted on the nacelle (the covering that houses all the generating components) of the wind turbine. Once installed, it emits continuous ultrasonic energy in the same frequency range as the bat’s bio sonar used to orient, forage and locate objects.
When bats enter the airspace where the deterrent units are operating, the ultrasonic energy essentially disrupts their bio sonar, making it difficult for them to find food sources and navigate their surroundings. This effectively minimizes bats’ interactions with the wind turbines. The ultrasonic field emitted by the Bat Deterrent System does not harm the bats and quickly dissipates beyond the turbine rotor sweep. The sound cannot be heard by humans and does not impact other wildlife or livestock.
Research study methodology & results
Duke Energy worked with researchers from Texas State University and NRG Systems to field test the Bat Deterrent System on 16 2-megawatt wind turbines located throughout Los Vientos III, IV and V in Starr County, Texas.
- Field testing was conducted on eight control and eight treatment randomly assigned turbines on a nightly basis between 2017 and 2018.
- The trials showed a 50% reduction in overall bat fatalities during the field testing period.
- The Brazilian free-tailed bat and hoary bat showed the greatest fatality reductions. The hoary bat, a bat species of recent conservation concern, showed a reduction of 78%.
Sara Weaver, PhD, biology lecturer at A&M, San Antonio, who led the Los Vientos study during her doctoral candidacy at Texas State University, said, “Our results from this robust, two-year study indicate that NRG’s acoustic deterrents significantly reduce Brazilian free-tailed bat and hoary bat fatalities. Based on these results, the technology is a promising tool for reducing bat fatalities at wind turbines.”
Funding for the research came from the Texas Parks & Wildlife Department and Bat Conservation International.
“Bats play an important role in our ecosystem and many species are facing unprecedented threats from disease and habitat alteration,” said Jonah Evans, mammalogist with the Texas Parks & Wildlife Department. “By taking voluntary steps to minimize impacts on our native species, Duke Energy is setting an example of proactive environmental stewardship. We are impressed by their leadership and encourage others in the industry to consider similar actions.”